Electron tube coupling circuit



April 4, 1950 E. BURTON wsc'mou TUBE COUPLING CIRCUIT 2 Sheets-Sheet 1 Filed Dec. 31, 1942 mws 0mm; 1m;

NETWORK FIG? M/l/ENTOR E. 7? BURTON A T TORA/EV April 4, 1950 E. BURTON 2,502,822

ELECTRON TUBE COUPLING CIRCUIT Filed Dec. 51, 1942 '2 Sheets-Sheet 2 INVENTOR E TBURTON ATTORNEY Patented Apr. 4, 1950 UNITED STATES-f ELECTRON TUBE COUPLING CIRCUIT Everett T. Burton, MillburmnNlJi, assignor to' Bell" Telephone= Laboratorie's',*:l Incorporate New York,-N; Y3, w-corporation of New York:-

Application. December 31, 1942; Serial No.i470,883

8 claims: (01. 178-544"); 1 2

This invention relates to wave translating aptwo voltages'whoseamplitudes are"dis'similalr-'in paratus, and-more particularly to such apparatus magnitude such that the" amplitude dissimilarity? for-transferring electrical waves fromanunbal-H is effectively transferred from-one circuit'to' anancedcircuitvto Va balancedicircuitior froma bale othercircuit. Thus; in effct'theforegoin'g other anced circuit to anunbalanced circuit. and further features involve difierential mixing asi An unbalanced circuit is one in which. one. side to frequency and -amplitudejrrespectively."

is at agiven polarity-with respect to ground while The invention will be readily understood from? the other side-isground-per se.. Abalancedlcirthe fol-lowing description'takentogether'with"the" cuit is-oneswhoseitwo sidesare at oppositepolaraccompanying' drawing, in which? itieslwithqrespectto ground..- Ground is com- In Fig. lis a box representationof a'wavetrans monly understood to include any steady potential. lating network interposed between'anunbalanced' accepted as a reference. Balanced or unbalanced circuit and a balancedcircuitj',

circuits contemplate a .rangeiof different condi- Fi'gJZ isa diagrarmnaticcircuit lllustratingi'a tions extending between completely balanced and specifld-enrbodir'nentofthe invention"involving completely unbalanced; 1 the translatinginetwork of Fig.1 1

The-present=invention involves electronic-apr- Fig. 2A 'is"'a**partial diagrammatic circuit of a paratus for translating voltages unbalanced-to. modificationthat'maybesubstituted-in"Figs;2, ground into voltages balanced to ground, and vice land? versa. Figr-B is a--partial diagrammatidcircuit that The main object of theinvention is to transfer maybe substituted'inl ig. 2; electrical Waves fromtamunbalancedlcircuititoia: Fig-"4 tea-diagrammatic circuit showing ant-- balanced network other embodiment of the invention;

Another object is to transfer electrical waves Figs;-5 and Gare-partial diagrammaticcircuits from an unbalanced circuit to an unbalanced netof modifications-that maybe substituted"irrFigsjf work. 2,4 and'7;

A further object is to transfer electrical waves Fig; '7 is-a diagrammaticcircuit"showingjan from a balanced circuit to a balanced networkuotherembodir'nent of thexinvention; and;

Still another object is to. transfer electrical Fig. 7A 'is aparti'al diagrammatic circuitbf'a: waves from a balanced circuitto an unbalanced modificationthatmay"be'substituted 'in'Fig. 17.:' network. In the-drawing the same referencenumeralsv In a specific embodiment the present invention are utilized'to'designatethe same elements'fap. interposed between'unbalanced and balanced cir.= pearing'in'th'e several figures: cuits comprises a pair oftelectronic tubes; each" Referring to Fig.1, an input circuit In oom-1t including a control grid;a cathode and an anode prises an'impeda'nce" I [,anadjustable contact-12 and aivoltage mixer individual to 'each'of the slidabl'e therealong andextended to ground'point electronic'tub'e's. Both control grids are extended |3,"'and"vo1tage sources Hand-MalOcated ati'bpe; to the unbalanced circuit, while eachanode is posite terminals'ofthe impedance II'. The. ad connected to a correspondingv terminal 'of one. of justable contact 1'2 serves tOiI app1y effectively the voltage mixers and eachcatliode .is applied difierent portions ofv the impedance II to round? to the opposite termina1: of the voltage mixer 'to w Thus, the inputbircuifllll may simulate an elecwhich the anode" of the other electronicf'tube" is tricalvoltagecomprisingtwoportions balanced" connected' The mid-points'of bO'th'VOltfiIgEiflfiX- orunbala'nce'd toground, and'at a given instanters are extended to the balanced circuit: provided with opposite signs. Obviously, the"iII'-i A feature of "the inventionfis that its effective putcircuit Illmay comprise'an source in which frequency range extends down to and including the voltage 'is balanced and/or unbalanced "to directicurrent. Another feature is that the two ground potential to any extent;"and"is so 'repre-i voltages to be transferred 'mayoriginate .in the. sented'for the purpose ofthisillustration: The same source ortwodifferent'sources;"and comvoltagespresent in the input circuit) and er: prise the same frequenc or different combina'e fective across terminals 8 and'9-are'u1timatelytions of-frequencies. Iri 'th'e latter 'connection amplified in the electronic'amplifie'r I5 and there-- voltage components"of-like"frequencyandtphase after supplied to a load I61 Referring to Fig.2, tend" to balanceout-"whi'le-nnlike voltage'com the electron-amplifier l5 may comprise a pairhof ponentslas to frequency) areefictivelftrans electron "tubes' ll "andI'B arranged impushpull ferred 'betweenthe unbalanced or balanced cir f and having its 'outputlbalanced to ground fpoten i uits." A furtherfeatureconcerns thetransferof tial' and appliedthroughanbutput transformer l9 to the load l6. A source of direct potential having a terminal 20a connected to a ground point serves to energize the anode-cathode circuits of both electron tubes I1 and I8, and through a resistor 2| to apply the same negative biasing potential to the control grids of both latter tubes. Thus, the amplifier tubes I1 and l8 are arranged to receive and amplify voltages having opposite polarities and balanced to ground potential.

In accordance with the present invention, the voltages present in the input circuit III are translated by the network 25, Fig. 1, into voltages balanced to ground potential which latter voltages are thereafter impressed on the input circuit of the amplifier |5. Referring to Fig. 2, the translating network embodies a pair of electron tubes 26 and 21, each of which embodies a control grid, a cathode, and an anode and arranged to supply a relatively low amount of power. The control grids of the tubes 26 and 21 are extended to the input terminals 8 and 9, respectively. The anode-cathode circuit of the tube 26 serially embodies cathode resistor 28, source 29 of direct potential having a point 29a applied to ground point, and anode resistor 30. The anode-cathode circuit of the tube 21 serially includes cathode resistor 3|, source 29, and anode resistor 32. The resistance value of the resistors 28, 30, 3| and 32 is of the same order of magnitude. The resistors 28 and 3| effectively apply equal magnitudes of negative biasing potential to the control grids of the tubes 26 and 21, respectively.

A pair of serially connected, equal resistors 34 and 35 has one outer terminal 36 extended over lead 31 to the anode of the tube 26 and an opposite outer terminal 38 applied over lead 39 to the cathode of the tube 21. A mid-point 40 of the serially connected resistors 34 and 35 is applied over lead 4| to the control grid of the tube l1. Thus, the serially connected resistors 34 and 35 together with the above-described connections thereto constitute effectively a voltage mixer. A pair'of serially connected, equal resistors 44 and 45 has one outer terminal 46 extended over lead 41 to ,the anode of the tube 21 and an opposite terminal 48 appliedover lead 49 to the cathode of the tube 26. A mid-point 56 of the serially connected resistors 44 and 45 is applied over lead 5| to the control grid of the tube IS. The resistance 4 value of the resistors 34, 35, 44 and 45 is preferably of the same magnitude. Thus, the serially connected resistors 44 and 45 and the connections thereto constitute effectively a voltage mixer. In

one illustration, the resistors 28, 30, 3| and 32 were of the order of 25,000 ohms; the resistors 34, 35, 44 and 45 were of the order of 500,000 ohms; and the effective mu of the tubes 26 and 21 was approximately unity.

In the operation of Fig. 2, let it be supposed that the voltage in the input circuit |0 comprises two portions unbalanced to round potential and applied to the input terminals 8 and 9. Let it be further supposed that when, at a given instant, the voltage portion on the terminal 8 is (+a), then voltage portion on the terminal 9 is (-b).

This means that, at the given instant, the voltage.

portions (+12) and (b) are simultaneously impressed on the control grids of the respective tubes 26 and 21. Due to phase reversal of the voltage portion (+a) in the tube 26, the voltage portion (-a) is impressed on the voltage mixer terminal 36 from the output circuit of the tube 26, and a voltage portion (-b) is directly impressed on the voltage mixer terminal 38 from the cathode of the tube 21. Due to phase reversal of the voltage portion (-1)) in the tube 21, the voltage portion (+b) is impressed on the voltage mixer terminal 46 from the output of the tube 21, and voltage portion (+a) is directly supplied to the voltage mixer terminal 48 from the cathode of the tube 26. As the mid-point 46 of the serially connected resistors 34 and 35 is connected to the control grid of the tube l1, the effective voltage value impressed on the control grid of the latter tube is As the mid-point of the serially connected resistors 44 and 45 is extended over the lead 5| to the control grid of the tube 8, the efiective Voltage supplied to the control grid of the latter tube is balanced to ground potential is supplied to the control grid of the tube l1, and a mean negative voltage value balanced to ground potential is impressed on the control grid of the tube l8. Thus, the voltage values,

and

Hung-(+11) considered together constitute an electrical voltage balanced to ground potential, regardless of whether the electrical voltage applied to the input terminals 8 and 9 is balanced or unbalanced to ground potential. These voltage values may comprise any frequency down to and including direct current. For the latter operation, the load |6 may be directly coupled to the output circuit of the amplifier IS in the usual manner as illustrated in Fig. 2A. In this connection, it is understood that the circuit portion shown in Fig. 2A is to be substituted in Fig. 2 for the circuit portion shown to the right of the line VV.

Fig. 3 is a modification in which the circuit portion between the lines X-X and Y-Y is substituted in Fig. 2 for the circuit portion shown between these same lines. In Figs. 2 and 3, the input terminal 8 is extended over lead 60 and resistor 6| to the control grid of electron tube 62, and over leads 60 and 63 to the voltage mixer terminal 36; while the input terminal 9 is extended over lead 64 and resistor 65 to the control grid of electron tube 66, and over leads 64 and 61 to the voltage mixer terminal 46. The tubes 62 and 66 arranged in push-pull function to reverse-the phaseof the wave portionsapplied thereto from the inputterminals 8 and 9. The effective mu ofi-the tubesiSZ and-86 is substantially unity. As the leads 39 and 49 are extended through the respective capacitors 158 and 69, the arrangement of Figs. 2 and 3 is efiective down to relatively low frequencies, but however not including direct current.

In the operation ofFigsLBZ and 3, let it be supposed at a given instant that the voltage portion (+11) effective on the input terminal -8 is simultaneously impressed on the control grid of the tube 62 and the voltage mixer terminal 35; and that the voltage portion (b) effective on the input terminal 9 is simultaneously impressed on the control grid of the tube '68 and the voltage mixer terminal 46. Sincethe tubes 62 and 66, Fig. 3, function essentially as phase reverses, the tube 62 impresses voltage portion '(a) over lead 49 to the voltage mixer terminal 48; and the tube 66 impresses voltage portion (+11) over lead 39 to the voltage mixer terminal 38. As the voltage portions (+a) andi-leb) are. impressed at the given instant on the voltage mixer terminals 35 and 38, respectively, then the efiective voltage portion is supplied to the control grid of the tube ll. As the voltage portions (a) and (-b) are impressed at the given instant on the voltage mixer terminals 48 and '46, respectively, then the efiective voltage portion is supplied to the control gridof the tube l8. As previously pointed out, these voltage portions constitute an electrical voltage balanced to ground potential, irrespective of whether the electrical voltage applied tothe input terminals 8 and 9 is balanced or unbalanced to ground potential. As pointed out concerning Fig. 2 the opposite effect takes place when voltage portions (-11) and (+12) are effectively present at a given instant on the input terminals '8 and 9.

In Fig. 4, the input terminal 8 is connected directly to the control grids .of electron tubes 10 and 13a while the input terminal 9 is connected directly to the control grids of electron tubes 11 and 12a. The individual pairs of tubes In and H and 12a and 13a areconnected so that the space current of the tubes 1c and 'Il flows in anode resistors 15 and '16, respectively, and the sp'ace 'current of the tubes 12a and'13a' flows in the anode resistors 11 and I8, respectively. The individual pairs of tubes 10 and 13a and H and 12c; are connected to the respective terminals Band 9. Adjustable contact 19 engaging the anode resistor I1 associated with the tube 12a is extended over lead 88 and capacitor 8| to the control grid of electron tube 82. Adjustable contacts 83 engaging anode resistor 18 is extended over lead 84 and'capacitor 85 to the control grid of electron tube 86. Leak'resistors 81 and-88 are connected between the control grids of the respective tubes 82 and 86 and ground point 89.

The anode of tube It! is applied over lead 90 to the voltage mixer terminal .33 while opposite voltage mixer terminal 38 is extended to the anode of the tube 82. The anode of tube H is applied over lead 9| to the voltage mixer terminal 46 while opposite voltage mixer terminal 48 is extended to the anode of the rtube 85. The midpoint 40 of the serially connected resistors 31 and is connected over ileadi ll :to thercontrolsgrid of .the tube l1; andpthet mid-rpoint 59 of .the serially connected mesistors 414 and 4.5 1s connected over lead 5 I :to the acontrol. grid. of the pressed onthecontrolgrids of the *tubes H and 12a. Due to phase reversal in the tube 10-,"-voltage portion (-a) is applied to the voltage mixer terminal 36; and due tossuccessive phase reversal in the tubes 12a and 82, voltage portion (b) is appliedtothe 'voltage'mixer'terminal '38. Due to phase "reversal in the tube "H, voltage portion (+b) is applied to the voltage mixer terminal 46; and due :to successive phase reversals in tubes 13a and 86, voltage portion (+a) is impressed on the voltage mixerterminal 48. As the voltage portions (-a) and (-1)) are impressed onlthe voltage mixer terminals .36and 38, respectively, at the given instant, then the effective voltage portion is supplied to the controlggrid 'of'the tube 11. ,As the voltage portions (+0.): and (+1)) are impressed'on the voltage'mixer terminals '48 and '46,. respectively, at the given instant, then the effective voltage portion portions (-a) and (+1)) are vefiectively present.

at a given instant on the input terminals 8 and 9. For direct current, the circuit portion of Fig. 2A is substituted for the circuit portion shown to the right of the line V-V in Fig. 4.

Thearrangements of-"Figs. 1,2, 3 and 4 may also be utilized to couple the-"input circuit it balanced or unbalanced to ground potentialto a load which unbalanced to" ground potential. In this connection, it is tobdunderstoo'd that the circuit portion shown tothe-right of the line Z-Z in'Fig. 5 is substituted for the circuit portion-shown'to'the right of line 'ZZ in'either Fig. 2 or 4. Referring toFig. '5, itis seen that the lead 41 is extended to the-control grid of'the tube l1, and the lead to the-control grid of the tube 18 is interrupted whichinterruption'in effect means that the latter'control' grid is .inefiective. Obviously, 'inFig. 5-the tube 18 may be omitted so that the load; is suppliedentirely from'the output of the tube I Pas shown in 6. In this connection it is understood'that -the circuit por-' tion ofFig. 6' may be substituted for the circuit portion shown to -the right 'of the line Z-Z in Fig. 4. In'Fig. 6, it is also noted that the load 16 is directly connecte'dvto'the output ofthe tube H for direct current operation. Fig. '-7 is generally'similar'to Fig. 2 except that it showsan arrangement in "which the voltages to be translated originate in two different sources 10 and H which may be balanced or unbalanced to ground and whose frequencies'extend over the ranges f1 to f2, and is to f4, respectively. If at a given instant, voltage (+a) is applied to the control grid of the tube 26 and voltage (+1)) is applied to the control grid of the tube 2'1, then an effective voltage portion balanced to ground is impressed on the control grid of the tube ll while an effective] voltage portion balanced to ground is applied to the control grid of the tube l8. Consequently, the resultant voltage which is simplified to [(+11) +(b) extending over both frequency ranges )1 to is and is to I4 is impressed n the control grids of the push-pull amplifier l5, Fig. 7, and is balanced to ground. It is noted in Fig. '7 that the potentiometers l2 and 73 are essentially the mixing resistors 34 and 35, and 44 and 45, respectively of Fig. 2 except the former embody sliders 14 and 75. It is also noted that Fig. '7 can be modified asshown in Figs. 2A, 5 and 6 and explained above regarding Fig. 2.

The potentiometers l2 and I3 in Fig. '7 serve to supply desired proportions'of the effective voltages (a) and (b) to the control grids of the respective tubes I1 and I8 as will be presently pointed out. Thus, when the sliders l4 and 15 are actuated to the respective terminals 16 and 19, the effective voltage at the slider I4 is (+1)) and at the slider 15 is (-b); when the sliders l4 and 15 are both actuated to the respective mid-points I! and 80, the effective voltage at slider 14 is and at the slider'15 is and when the sliders 14 and 15 are both actuated to respective terminals 18 and 8|, the effective voltage at the slider 14 is (-a) and at the slider 15 is (+a). At each of these three terminals, or any other terminals of the potentiometer sliders l4 and 15, the resultant voltage across both sliders as above pointed out is balanced to ground. The reverse takes place when the voltages (a) and (b) are impressed on the input terminals 8 and 9, Fig. 7.

Fig. 7 also serves to mix two input voltages which originate in the independent sources "It and H, or in related sources 82a. and 82b as indicated in Fig. 7A which latter sources are essentially a duplicate of the input circuit It, Fig. 2. In Figs. 7 and 7A the voltage components of like frequency and phase balance out while the components ofdifferent frequencies and phase appear acros the sliders l4 and 15 as will be presently pointed out. Suppose, for. example, that voltage (+a) is of one frequency and phase, and the voltage (+b) is of a difierent frequency and phase; and further that at a given instant voltage (+a) is impressed on input terminal 8 (-a) (+a) (+b) 2 is On mid-point I1; voltage (-l-a) is on terminal 8|; voltage which simplifies to is On terminal 19; voltage which simplifies to is on mid-point and voltage which simplifies to (b) is effective across the mid-points l1 and 80 on which the sliders 14 and 15, respectively, are positioned.

Thus, the voltages (+11.) and (a) of like frequency and phase balance out so that the resultant voltage (1;), which i only the voltage of the different frequency as above mentioned; is effective across the sliders l4 and 15. The foregoing operation involves, in effect, the differential mixing of two voltages which include common and different frequencies.

Figs. 7 and 7A also serve to mix two input voltages comprising a first voltage (-l-a) of certain frequency ,fl and a second voltage (-{-an) of the certain frequency f1, where n is a multi-' plier representing the amplitude difference-be tween the two voltages (+a) which may be balanced or unbalanced to ground. When at a given instant, voltage (+a) is applied to input terminal 8 and voltage (+an) to input terminal 9, then voltage (-a.) is on terminal 18; voltage (+an) is On terminal 16; voltage is on the mid-point 1'! and is balanced to ground; voltage (-l-a) is on terminal 8|; voltage (an) is on the terminal '19; voltage is on mid-point 80; and the resultant voltage gun-1) (1- cit-"acn I) is effectiveacross the mid-points 11' and 80 on which the sliders l4 and '15, respec t'ive'ly, are positioned, and is balanced to ground. This resultant voltage of frequency. f1 compriseseffectivelythe amplitude difference between the input voltages (cc) and (an). The foregoing operation involves in effect the differential mix-- ing of two voltages of the, same frequency as to' theamplitude difference therebetween.

What. is claimed is:

1., A"wave translating system comprising apparatus consisting of a pair of electron tubes, each including a control grid, arranged in pushpull to amplify electrical waves having portions of opposite signs and balanced to ground potenti'aLa source to supply'electrical waves having portions of opposite signs and balanced or unbalanced to ground potential, and means interposed between said amplifying apparatus and said" source to change'thewave portions supplied by said source into wave portions having opposite signs and balanced to ground potential and to apply said latter wave portions to the input circuit of said amplifying apparatus, said means comprising four. furtherelectron tubes arranged in pairs each of said latter tubes including a control grid, a cathode, and an anode, circuit meansto-connectsaidsOurce to'the control grids ofone tub'ein each-pair of said further tubes such that eachdnputterminal of individual sign of said source is connected to two control grids, a pair of serially connected resistors individual toeach pair of said further tubes, other circuit means to connect the anodes of one pair of said further tubes to certain terminals of said pairs of resistors, further circuit means including another pair of electron tubes to connect the output circuits of the other pair of said further tubes to other terminals of said pairs of resistors, said certain and other terminals of the individual pairs of serially connected resistors being effectively connected across said source, and additional circuit means to connect the mid-point of each pair of serially connected resistors to the control grid of one of said amplifying tubes.

2. In wave translating apparatus, a circuit for supplying signal waves comprising two portions having different polarities, a circuit for receiving signal waves, and means interposed between said supplying and receiving circuits for translating each of the two wave portions into two further wave portions and transmitting said last-mentioned wave portions to said receiving circuit, comprising a pair of electron discharge tubes each having a control electrode, a cathode, and an anode, circuit means for connecting said supply circuit to the control grids of said tubes, an impedance associated with each tube, said impedance having a resistance value that limits the flow of current therein to a negligible amount, further circuit means for connecting the cathode of each tube to the anode of the other tube and including the impedance associated with said lastmentioned tube in series therebetween whereby two further wave portions of the same sign are combined, and additional circuit means for connecting said receiving circuit to a middle point on at least one of said impedances for transmitting at'least one of the respective combined wave portions to said receiving circuit,

3. In wave transferring apparatus, a source for supplying signal waves extending over a certainfrequencyrange, a source for supplying signal waves extending over a difi'erentffrequency rangeyra circuit for receiving both the certain and different signal waves, and means for trans-g ferring the signal waves from both said sources to said receivingcircuit, comprising means including, two pairs of output terminals for dividing 5' each of the certain and different waves into two further wave portions, a pair of impedancenetworks, each being'connected between two'of' said. output, terminals comprising one terminal ofv each of said two pairs thereof, each network combin 10 ing two of saidfurther wave portions to provide;

one resultant wave portion, said last-mentioned two further wave portions including one further wave portion dividedifrom each of the certain and different waves, and circuit means for connecting said jreceivin'g circuit to different wave potential pointsionone or both of said networks whereby one orbotlr of, the resultantwave por-' tions or varying magnitude and varying polarity are-applied to said receiving circuit.

'- 4. In a wave translating system, a circuit for supplying-signal waves having a certain frequency, a circuit for supplying signal waves in cluding the-certain waves and waves havingia difierentfrequency, a circuit for receiving signal, waves, and means for connecting said two sup? plying circuits and said receiving circuit whereby thedifierent-waves only are supplied to said re;

ceiving circuit, comprising. a pair of electron dis-r charge tubes eachiincluding a control electrode "a"catho'de; and 'an anode; circuit means for'con necting each supply circuit to the control electrode of one tube, an impedance associated with each tube, other circuit means for connecting the cathode of each tube and the anode of the other tube across the terminals of one impedance whereby portions of the certain waves with opposite polarities and a portion of the different waves with a predetermined polarity are supplied to each impedance, said certain wave portions balancing 40 out in the respective impedances and said different wave portions of predetermined polarities remaining therein, and further circuit means for connecting the receiving circuit to a preselected point of wave potential on one or both of said 5 impedances to apply to said receiving circuit one or both of the diiferent wave portions of the predetermined polarities.

5. In a wave translating system, a circuit for supplying signal waves of certain amplitude, a

circuit for supplying signal waves of a different amplitude, a circuit for receiving signal waves, and means for applying to said receiving circuit signal waves having an amplitude which is substantially equivalent to the diiference between the certain and different amplitudes, comprising across the terminals of one impedance whereby portions of the certain and different signal waves with opposite polarities are supplied to each impedance to produce a resultant wave portion having a certain polarity and an amplitude substantially equivalent to the difference between the certain and different amplitudes, and additional circuit means for connecting the receiving circuit to a-middle point on at least one of said impedances for applying at least one of the resultant wave portions having the certain 11 polarity and the difference amplitude to said re-v ceiving circuit.

6. A wave transferring apparatus according to claim 3 in which said dividing means comprises a pair of electron discharge tubes each of which includes a control electrode, a cathode, and an anode, each of said wave sources is connected to the control grid of one of said tubes, and each of said networks is connected between said two output terminals which include the anode terminal of one tube and the cathode terminal of the other tube.

, 7. A wave transferring system according to claim 3 in which each of said networks comprises a potentiometer including a resistor and a contact adjustable along the electrical length thereof, each of said resistors is connected between said two output terminals which comprise one terminalofeach of said two pairs thereof, and said circuit means comprises circuit connections extending from said receiving circuits to-one or both of said adjustable contacts. I

'8. In wave translating apparatus, a circuit for supplying signal waves comprising-two portions having opposite signs, means for translating each of said signal wave portions into two further wave portions having opposite signs, said means including a plurality of electron devices each having a control grid, a cathode, and an anode, further means for connecting said supply circuit to 12 the control grids of at least two of said electron devices, a plurality of output terminals, and additional means for efiectively connecting the cathodes of said devices to certain output terminals and the anodes of said devices to other output terminals, a plurality of impedances each connected between one of said certain output terminals and one of said other output terminals for combining said further wave portions into two resultant wave portions having opposite signs, each of said impedances having an effective resistance that limits the amount of current flow therein to a negligible value, a receiving circuit,

and another means for connecting said receiving circuit to at least one of said impedances at a point intermediate said certain and other output terminals to which the respective impedances are connected for supplying at least one of said re-, sultant wave portions to said receiving circuit.

EVERETT T. BURTON.

REFERENCES CITED The following references are of record in the file of this patent:

UNITED STATES PATENTS Number Name Date 2,101,438 Lindenblad Dec. 7, 1931 2,201,345 Percival May 21, 1940 2,296,920 Goodale Sept. 29, 1942 

